1. Field of the Invention
The present invention relates to a primer composition and, more particularly, to a primer composition for use in a priming process applied when an adhesive such as a sealant and adherends such as concrete, woods, metals, plastics and others are adhesive bonded together.
2. Description of the Prior Art
When an adhesive such as a sealant used mainly for building constructions is filled into joints of adherends including concrete, woods, metals and plastics, the priming process is often applied to the adherend, for the purpose of increasing adhesive strength and adhesive durability.
A primer composition usable for the purpose of this kind is disclosed in, for example, Japanese Laid-Open Patent Publication No. Hei 3(1991)-6274, which discloses a primer composition comprising a reactant of a trimer of isophorone diisocyanate with an active-hydrogen-group-containing resin; a silane coupling agent; and a curing-catalyst-containing organic solvent solution. Also, Japanese Laid-Open Patent Publication No. Hei 6(1994)-329925 discloses a primer composition comprising polyisocyanate modified by mercapto silane having an alkoxy group; polyisocyanate having one or more isocyanurate rings and two or more isocyanate groups; at least one of alkoxy silane and .gamma.-chloropropyl trimethoxy silane; and chlorinated polymer dissolved in an inert organic solvent.
However, any of these known primer compositions contain an organic solvent. An aqueous primer composition containing no organic solvent for purposes of this kind has not been known so far.
On the other hand, from the viewpoints of global environment, safety, hygiene and the like, reduction of the amount of use of the organic solvent has recently come to be urgently necessary, for the reason of which development of an aqueous primer composition has been being strongly desired for a primer composition for use in the priming process for the adhesive such as a sealant.